Ben-Avi was born in Cleveland, Ohio on May 26, 1923 to Sophie and Paul Sampliner. Her father was an organizing founder of the Anti-Defamation League of B'nai B'rith and served on its national commission for 24 years. He was a member of the New York City Anti-Crime Commission and the New York State Commission Against Discrimination. Sampliner was also a co-founder of National Periodicals Publications, and the Founder and President of the Independent News Company. From 1937-1967 he was co-owner of the famed DC Comics.[1]

Ben-Avi attended Smith College. She was an avid reader and art lover, and she collected many works of fine art. She was married to Avrum Ben-Avi, a clinical psychologist, for 36 years. During their marriage they traveled widely, primarily in Europe. The marriage ended in divorce, but the two remained on good terms until their deaths. Joan is survived by her brother, Philip Sampliner, her son Jason Ben-Avi, and her daughters Sigrid Balmer, and Nina Ben-Avi Schreiber; two sons-in-law: Reg Balmer and Marc Schreiber; as well as four grandchildren: Alice and Sarah Balmer, and Julia and Emma Ben-Avi.[2]